|
Aims of 'Ring' Vaccination
|
|
FMD control must be considered on a regional basis. This fact was recognised most
recently by the European Union, and was the motivation for the changes in European FMD
control strategy before the introduction of the Single Market on 1 January 1993.
In the first instance FMD-free countries would attempt to control an outbreak of FMD
through 'stamping out', with slaughter of affected and in-contact susceptible livestock
and the imposition of movement restrictions. However, in certain circumstances, where an
outbreak threatened to become extensive, in densely populated pig production areas where
there was a high-risk of airborne spread or for welfare reasons, strategic 'ring'
vaccination could be used. Therefore, FMD-free countries now maintain Emergency FMD
Vaccine Banks, often cooperatively with other countries of similar FMD status.
These banks store FMD vaccine, either pre-formulated or more commonly as frozen,
concentrated antigen. The essential elements of the emergency FMD vaccine banks are
immediate access to highly potent vaccines from antigens of known potency and spectrum of
activity, a facility for rapid re-formulation of the vaccines under Good Manufacturing
Practice (GMP) conditions and a capacity for efficient bottling, labelling and despatch.
The aim of the 'ring' vaccination would be to reduce the risk of further spread of the
outbreak and to dampen down the amount of virus generated. Decisions would be made on
when and where to vaccinate with the assistance of the airborne prediction models and
expert systems available to the epidemiology team.
The objective of a vaccine bank is to guarantee rapid access to vaccine of known
quality. In the case of FMD this is especially important because of the ability of the
disease to spread rapidly and the recent contraction of the FMD vaccine market. There
are three international vaccine banks in existence and many national banks around the
world. All member countries of these banks are FMD-free and have a 'stamping out' policy
for FMD control in the first instance. Member countries would only resort to emergency
vaccination when an outbreak threatened to become extensive due to livestock density or
geographical considerations, or where valuable breeding stock was involved. .
|
